I agree that one of the stumbling blocks may be your moving in with his parents - that's not at all the same as setting up your own place, you won't get a true position of "coping with living together" at all, all you are doing is sleeping together at his house, still living with his parents. Your parents will no doubt ask why he's not moving into their house, instead.
f you are going to do it, you need to cost out what it'll cost you to rent even the tiniest flat - rent, insurance, food, saucepans, etc. - and see if you can afford it. Yo